For video or stills?
Here's a variety of underwater housings for video cameras:
2) Click on the "Underwater with Your Camera.."
- or -
1) go to ebay
2) search for "underwater hosuing" http://search.ebay.com/underwater-housing_W0QQsokeywordredirectZ1QQfromZR8
I own the Sony SPK-PC4 (for video) and it works well. My only complaint is that I cannot fit a wide angle lens in the housing.